New York City's mass transit system has ground to a halt after residents in low-lying areas were ordered to to evacuate ahead of hurricane Sandy.

With the super storm expected to make landfall on Monday, officials in the city are taking no risks, shuttering schools and urging people to seek alternative accommodation away from lower Manhattan and threatened parts of Brooklyn and Queens.

"If you don't evacuate, you are not only endangering your life, you are also endangering the lives of the first responders who are going in to rescue you," Mayor Michael Bloomberg said at a news conference Sunday. "This is a serious and dangerous storm," he reiterated amid talk from some residents that city officials were over-reacting.

Earlier, New York governor Andrew Cuomo announced the emergency suspension of subway and bus services from 7pm Sunday. The transit shutdown will last until Wednesday under the current plan. Officials said services would resume operations about 12 hours after Sandy has passed through the city.

"If it turns and moves off, great. Really great. But if not then we will be prepared for it," Cuomo said at a press conference Sunday.

The governor added that a decision on New York's network of bridges and tunnels to and from Manhattan would be made on a case-by-case basis.

Similar measures were brought in to shut down New York City's transit system ahead of hurricane Irene last September.

On that occasion, some 370,000 residents in low-lying areas in the city were evacuated as a precaution.

A similar plea for people to leave at-risk areas has been issued, with Bloomberg warning that a storm surge of six to 11 feet was expected.

But he confirmed that no action would be taken against those who refused to leave.

For many, a more pressing matter was stocking up on food ahead of the storm.

In the fashionable Williamsburg neighbourhood of Brooklyn, residents lined up at the Key Food store to stock up on food, beer and cereal.

Holding a single basket filled with peanut butter, bread, jelly, granola, pasta and hummus, Jordan Breighner admitted this is the most food he can remember buying in one go.

"Thankfully I am not on the first floor," he says. Breighner, who was in New York last year when hurricane Irene failed to make as big a mark on the city as some had feared, said he was concerned people might not take this storm seriously. "I'm not panicking but I'm prepared."

Others seemed to be setting up for a long-haul. Two 20-something women were buying two 16-roll packs of toilet tissue. "I haven't done any shopping for a while," one said, looking embarrassed. "I wonder if she bought a lot of coffee too," quipped another shopper.

Elsewhere in the city, people were making preparations for the city shutdown.Businesses were closing early, nursing homes were making plans to evacuate their residents, and people were beginning to take the official warnings seriously.

In some parts of lower Manhattan there is only a few feet between the usual high water level and the street, leading to some residents putting out sandbags in an attempt to keep back any flood waters.

In the well-healed Tribeca district of lower Manhattan, up-market grocery store Whole Foods Market was doing a roaring trade Sunday.

Grace Lin, who lives just outside the evacuation zone ordered by the mayor said she was taking in friends from nearby. "There will be four adults and four children, and we are two adults and two children, so it's going to be pretty cosy," she said.

Residents of the area had made similar preparations for Irene. But Lin said this storm appeared to be worse and that she had particular concerns about power outages.

"People are taking it more seriously than last time. The biggest issue for our friends is the elevators not working, not the flooding."

Others in lower Manhattan, however, were determined to stay put. Kevin Heeney, 28, was stocking up with bottled water, but had no plans to move out: "We're going to stick it out," he said.

Emerging from Whole Foods laden with bags of groceries, Danny and Laura Fletcher, a British couple who had just moved to the city, were scepical of the reaction of New Yorkers. "We've just bought a big roast lunch," said Danny Fletcher. "I don't think it's going to be that bad. But it's panic stations in there," he said.